2007 eruption, earthquake and tsunami

On 2 April 2007, the Solomon Islands were struck by a major (8.1 magnitude) earthquake followed by a large tsunami.
The eruption possibly triggered the small eruption of Kavachi volcano observed at the same time.

[verstecken]The 8.1 magnitude earthquake had a hypocenter 349 kilometres (217 miles) northwest of the island's capital, Honiara, and at a shallow depth of 10 km.
According to the United States Geologic Survey the earthquake struck at 20:39:56 UTC on Sunday, 1 April 2007. More than 44 aftershocks of a magnitude of 5.0 or greater were recorded in the region during the following 3 days.
The quake triggered a tsunami which mainly affected the small island of Gizo and was initially reported to be several metres high (up to 5-10 meters according to various sources).
At least 52 people were killed by the resulting tsunami and more than 900 homes were destroyed, leaving thousands of people homeless.
Land thrust from the quake has extended the shoreline of Ranongga island by up to 70 m according to local residents. As a result, many once pristine coral reefs are now exposed on the newly formed beaches.
Eruption of KavachiThe earthquake might have triggered a small eruption of Kavachi volcano. The eruption was first noticed by local residents who reported noises and mentioned that at the time of the earthqake, Kavachi emitted an eruption column.
During a survey on 6 April, the water above the active vent was found vigorously upwelling. Divers mapped a muddy plume of discolored mud- and sulfur-laden water several hundred meters wide and at least 3 km in length downcurrent. Water temperatures were measured at 40°C in the subsurface plume, which corresponded to normal temperatures found at Kavachi since 1999.
The only explosive activity observed or felt was occasional thudding detonations and sea-surface percussions, with shockwaves producing spray and billows of ash-laden water. There was no significant explosive eruption column or signs of ejected pyroclastic materials.

2004 eruption

2001-2002 eruptions

Kavachi volcano was active throughout most 2001-2003 and produced a new island in October-November 2002. A particularly intense phase was noted during infrequent visits between August to mid-September 2001 when there were daily explosions that breached the surface. During August ash and volcanic blocks were observed being ejected up to about 400 m above the surface, and at night, lava glow was visible from the coast of Gatokae (Nggatokae) Island 32 km NE of Kavachi.
In January 2002 the summit of Kavachi's summit was at 60 m depth. At the surface, brown muddy bubbly upwelling water as well as sulfur were observed at the surface. A large stain of discolored water extended many kilometers from the vent. My 16 March 2002 the summit had grown to a depth of -34 m. Occasional surtseyan explosions were seen from Gatokae Island.
In October and November 2002 Kavachi formed a new island that reached 10-15 m above sea level. The island was still visible in August 2003, but had disappeared in September, when the summit of the volcano was measured at 32 m below sea level.

2000 shallow submarine eruption

Scientist onboard the Australian research ship R/V Franklin observed an eruption of Kavachi on 14 May 2000. The summit of the volcano was at only 2-5 m below the sea surface and there was intense Surtseyan activity with explosions producing rooster-tail jets of ash, steam, blocks and incandescent lava blocks that were thrown up to 70 m height. The ash plume reached about 500 m height.

1997 eruption

A Solair pilot reported eruptions of Kavachi volcano on 16-17 January 1997, with ash plumes reaching 2100 m altitude.
On 29 January the sea water near the volcano was discolored and dirty, but no eruptions.

1991 eruption forming new island

The eruptions of Kavachi volcano in 1991 formed a new temporary island first observed on 45 May during a Western Pacific Air helicopter overflight. The island was 300x150 m wide, 30 m high and contained a lava lake of 50 m diameter in its crater.
The location of the new island was about 3 km NE of Kavachi's summit, placed at 9.00°S, 157.97°E.
On 5 June, a vigorously active lava fountain reaching about 25 m high and producing an ash plume more than 2,500 m height were observed. After a phase of powerful explosions, the eruption ended in late June and the island disappeared quickly.

1985-86 eruptions

A new eruption at Kavachi volcano started on 9 December 1985. During an overflight on 31 Dec, ejections of rock, mud and steam to a height of 30 m above the ocean surface were observed. The eruption did not form an island and ended by around 3 March 1986.
A second eruption occurred in July 1986, when explosions up to 60-90 m height were observed, with incandescent lava blocks in the inner parts of the ejections. The July eruption only lasted 2 days.

1980-81 eruption

A new small eruption of Kavachi was observed on 7 October. A mixture of water, steam, and blocks were ejected intermittently to more than 100 m above the ocean surface and the sea water above the vent was slightly discolored.
The eruption continued until after 25 February 1981 and ended sometime before mid September 1981.

1978 eruption

On 21 June 1978, a new eruption of Kavachi volcano was discovered. During an overflight, a new 1 meter height island was found that had a flat circular shape and measured 30-50 m diameter. There were occasional weak explosions ejecting ash and scoria, and the perimeter of the island was steaming.
On 14 July 1978, the island N-S elongate island and had a central cone about 30 m high. Strombolian activity occurred from the central vent, ejecting scoria to up to 400 m height. A lava flow was observed running down the S flank. A small secondary vent formed near sea level on the E coast.
By 16 July 1978, when the island could be observed again, the S half of the island, including the central vent, had dropped along an E-W fault. There was a steep scarp that formed the new S edge of the island at its place. Eruptive activity continued with infrequent explosions from the secondary vent on the E coast.
When next observed on 28 July, the eruption had ended. A small rocky island, about 15 m long, 5 m wide and no more than 3 m high remained at the eruption site. The island was expected to be destroyed by wave action within a few days to a few weeks.
Source: Smithsonian / GVP monthly activity updates

1977 eruption

A small eruption occurred at Kavachi volcano in July 1977, producing small Surtseyan explosions at about 30 second intervals.

1976 eruption: new island

Following 6 years with no known activity, a new eruption of Kavachi was first observed on 24 August 1976. A fountain of water and volcanic ejecta reached 30 m height.
The eruption quickly increased and explosions reached about 60 m on 4 September, when a change of the eruption column from white steam and spray to "smoke" (=ash) was noted. Eruption height on 7 Sep was 90 m, and a cone surfaced 1.5-3 m above sea level later that day and was seen erupting lava. The next day, the cone had grown to 9 m above sea level and measured 40 m across. Liquid lava was seen from its vent and a lava flow poured to the NW. Strombolian activity threw incandescent bombs to 150 m height.
The eruption was weaker on 9 September and the island showed signs of breaking up by wave erosion. The lava flow ended between 9-11 Sep, but explosions continued at intervals between 30 s - 2 minutes.
On 13 October, explosions continued, but the island had disappeared. At the site, the sea was discolored over an area of 100 m. Ejections reached about 30 m height.
The eruption ended probably in late October.

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